1. Field of the Invention
This invention relates to methods of etch manufacturing elements such as infrared detector elements, in which at least one narrow aperture is etched in a substrate or body. The body may comprise an infrared-sensitive material, particularly but not exclusively, cadmium mercury telluride. However, it is also recognised by the applicants that such an etching process may be applied to other electronic devices, for example those comprising other semiconductor materials.
2. Description of the Prior Art
For many years it has been known to use buffered chemical (isotropic) etchants in the manufacture of electronic devices, including semiconductor devices and infrared detectors. Published United Kingdom patent specification GB-A-1 559 473 describes the manufacture of infrared detector elements of cadmium mercury telluride in which separate body portions are formed for each element by etching slot-shaped apertures through cadmium mercury telluride bodies mounted on a temporary support. On the bodies, an etchant resistant mask of photoresist is provided having windows where the slots are to be etched. In a particular embodiment, the width of the slots is 30 um (micrometers) as finally etched through bodies which themselves have a thickness of 8 um. It is noted that, even if the thickness of the bodies is reduced to 6 um, it is not readily possible to achieve a separation of less than 12 um using such an etchant treatment. For this reason, the separate detector elements defined by this etching treatment in the embodiment of GB-A-1 559 473 are formed on a temporary support from which they are subsequently removed and assembled, with a closer separation, on a substrate of the detector device.